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Virus cocktail gets the jump on pest rabbits

Farmers and landowners across Australia have gained an advantage in the fight against pest rabbit populations through the combination of two biological controls currently available in Australia.

A joint research project involving Flinders University, the Department of Primary Industry and Regions SA (PIRSA), the University of Adelaide, the University of Canberra and the Centre for Invasive Species Solutions in examining the growing immunity of rabbits to the myxoma virus and the rabbit haemorrhagic disease virus (RHDV), discovered a positive interaction between the viruses.

Since the release and establishment of rabbits in Australia in the mid-19th Century, people have had to put up with the ecological and financial disasters caused by pest rabbits. The estimated economic benefit to agriculture from the introduced biocontrols to reduce pest rabbits – myxoma virus in 1950 and rabbit haemorrhagic disease virus (RHDV) in 1995 - now exceeds $70 billion.

After analysing twenty years of data collected by PIRSA Biosecurity SA at Turretfield north of Adelaide, researchers have discovered that the combination of the well-known myxoma virus followed by RHDV provides a greater reduction in rabbits immune to the myxoma virus.

Research Officer at PIRSA Biosecurity SA, Dr David Peacock said it is believed the research is the the first in the world to detect this interaction between the myxoma virus and RHDV.

“We also believe it is the first to record such a positive benefit from one viral biological control agent towards another,” he said. “It’s a rare demonstration of how an unprecedented, long-term monitoring programme combined with advanced ecological modelling has identified such a novel and important effect.”

Dr Louise Barnett from the Global Ecology Laboratory at Flinders University said that for

the first time there is now hard evidence that this specific combination of these two well-known diseases is more effective in reducing pest rabbit abundance.

“This will provide agencies and landowners with more bang for buck during their rabbit control programs,” she said. “Pest rabbits compete with livestock for food and continue to cause enormous environmental and financial damage across Australia, so large-scale efforts to release viruses that limit the population are essential.

“They continue to pose a challenge for land-management agencies around the world, and our research shows that the cocktail of biological controls reduces rabbit numbers even further than expected.”

Pest rabbits cost the Australian economy up to $250 million each year in lost production and millions more in pest control.

But Dr Barnett said knowing that the combination of the myxoma virus before RHDV can be a more efficient weapon when it comes to reducing the pest rabbit population has major implications for land owners and farmers around the world.

“Potentially, disease outbreaks could be timed more carefully to ensure the death rate rises,” she said. “Our research indicates that introducing RHDV after rabbits have been exposed to myxoma increases their mortality rate by another 10 percent.”

Flinders University Professor Corey Bradshaw said data collected by PIRSA Biosecurity SA were analysed by a team of researchers at Flinders University, in conjunction with researchers at Biosecurity SA, The University of Adelaide and University of Canberra, to test whether the two viruses were more effective in tandem.

“The team tested the theory that exposing rabbits to one disease altered the likelihood the population would die from the second virus, and that’s when we discovered the mortality rate from RHDV was higher than expected when a rabbit had already been exposed to myxoma virus,” he said.

The discovery has global implications with European rabbits causing environmental and agricultural damage in places such as Australia, the United Kingdom, New Zealand and in parts of South America. The discovery will also assist efforts to save the rabbit in its natural range in Europe and support Australia’s search for other rabbit biocontrols. Futher implications for other biological control programs are yet to be explored.

This work has been published online in the Journal of Applied Ecology:

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